As mentioned in the research proposal, in order to achieve the objectives of this research project, entire project was divided into work packages. The project initiated with computational screening of the potential TADF emitters and host materials and evolved with organic synthesis, chemical characterization, photophysical and electrochemical studies, and finally OLED device fabrication and testing. The project further categorized in terms of TADF emitters and host materials. An up-to-date overview of entire project and main results is as follows:
(1) 2nd generation TADF-OLED emitters: In this work, we have designed and synthesised four derivatives of a well-known green TADF emitter, 2CzPN and the effect of phosphine chalcogenide on their photophysical and optoelectronic properties was studied. Phosphine oxide-substituted carbazole derivatives were used as donor moieties to strategically blue shift the emission of 2CzPN. This work has been completed and a manuscript is under preparation.
(2) High triplet energy ambipolar TADF-OLED host materials: In this work, we have designed and synthesized four derivatives of triphenyl phosphine oxide substituted with carbazole and 9,9-dimethyl acridan. These materials found to be possess high triplet energy and ambipolar charge transport character; and eventually have turned out to be excellent host materials in terms of suppression of efficiency roll-off of TADF-OLED devices. With these results, we have been able to successfully achieved one of the objective of this research proposal. This work has been published in Chem. Lett., 2019, 48, 1225-1228.
(3) TADF-OLED emitters based on through space charge transfer (TSCT): In this work, a number of TADF emitters based on charge transfer through space were designed and screened through computation simulation. Acenapthene has been chosen as bridging unit to link donor and acceptor in co-facial arrangement. The synthesis of some these derivatives has been completed and photophysics in under investigation, while others are still under preparation.
(4) Effect of heavy-atom on TADF-OLED host materials: 1,3-Bis(cabazolyl)benzene (mCP)_is well-known host material for TADF-OLED. In this work, we designed and synthesized halogen (X = Br & I) substituted mCP derivatives to study the effect of heavy atom on performance of TADF emitters based OLED. The synthesis of Br-substituted mCP derivatives has been completed while synthesis of I-substituted mCP derivatives is under preparation.
(5) Electrochemiluminescence (ECL) in TADF emitters: As part of an established collaboration between EZ-C and Prof. Zhifeng Ding at Western University, Canada, we have observed highly efficient ECL properties in some of the newly synthesised TADF emitters. Further investigation into this observation is in progress.
